Sewer pipes at times are plugged, especially in order to perform pneumatic pressure tests. In the construction of residential and commercial buildings it is often necessary to test the gravity sewer lines for their tightness and operability. In order to perform these tests, all ends of the sewer pipe should temporarily be tightly plugged. During the plugging, air under pressure is put into the pipe, and the plug is expected to be able to hold that air pressure. In order to perform such a test, the plug may be inflated. The purpose is to determine whether the pipe does leak. After the test, the plug is removed from the pipe, so that further work can be continued or completed.
Several types of pipe plugging devices have been proposed for testing such pipeline networks as sewer lines.
Currently and historically, a series of rounded ribs have been incorporated on the outer periphery of such a plug, in order to provide a surface that enables the application of pressure of the plug on the inner surface of the host pipe, without causing the plug to move. These rounded ribs have been intended to resist slippage, but in the past the rounded ribs have resisted the slippage only to the extent of being able to hold without slippage a back pressure approximately equal to about 56% of the interior inflation pressure of the plug.
An object of the present invention is to make it possible for the plug to hold pressures equal to the inflation pressure of the plug, without slippage of the plug. These rounded ribs have not had the ability to hold the plug stationary under such pressure. Thus, an object of the present invention is to resist head pressures without slippage for pressures that are higher than would conventionally have been put into the plugs.
Another object of the invention is to provide a novel rib structure and a novel system of circumferential suction rings that improve the ability of the plug to resist head pressures.